 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.text.edits;

 import java.util.ArrayList ;
 import java.util.List ;

 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.IDocument;

 /**
  * This class encapsulates the reverse changes of an executed text
  * edit tree. To apply an undo memento to a document use method
  * <code>apply(IDocument)</code>.
  * <p>
  * Clients can't add additional children to an undo edit nor can they
  * add an undo edit as a child to another edit. Doing so results in
  * both cases in a <code>MalformedTreeException<code>.
  *
  * @since 3.0
  */
 public final class UndoEdit extends TextEdit {

     UndoEdit() {
         super(0, Integer.MAX_VALUE);
     }

     private UndoEdit(UndoEdit other) {
         super(other);
     }

     /*
      * @see org.eclipse.text.edits.TextEdit#internalAdd(org.eclipse.text.edits.TextEdit)
      */
     void internalAdd(TextEdit child) throws MalformedTreeException {
         throw new MalformedTreeException(null, this, TextEditMessages.getString("UndoEdit.no_children")); //$NON-NLS-1$
 }

     /*
      * @see org.eclipse.text.edits.MultiTextEdit#aboutToBeAdded(org.eclipse.text.edits.TextEdit)
      */
     void aboutToBeAdded(TextEdit parent) {
         throw new MalformedTreeException(parent, this, TextEditMessages.getString("UndoEdit.can_not_be_added")); //$NON-NLS-1$
 }

     UndoEdit dispatchPerformEdits(TextEditProcessor processor) throws BadLocationException {
         return processor.executeUndo();
     }

     void dispatchCheckIntegrity(TextEditProcessor processor) throws MalformedTreeException {
         processor.checkIntegrityUndo();
     }

     /*
      * @see org.eclipse.text.edits.TextEdit#doCopy()
      */
     protected TextEdit doCopy() {
         return new UndoEdit(this);
     }

     /*
      * @see TextEdit#accept0
      */
     protected void accept0(TextEditVisitor visitor) {
         boolean visitChildren= visitor.visit(this);
         if (visitChildren) {
             acceptChildren(visitor);
         }
     }

     /*
      * @see TextEdit#performDocumentUpdating
      */
     int performDocumentUpdating(IDocument document) throws BadLocationException {
         fDelta= 0;
         return fDelta;
     }

     void add(ReplaceEdit edit) {
         List children= internalGetChildren();
         if (children == null) {
             children= new ArrayList (2);
             internalSetChildren(children);
         }
         children.add(edit);
     }

     void defineRegion(int offset, int length) {
         internalSetOffset(offset);
         internalSetLength(length);
     }

     boolean deleteChildren() {
         return false;
     }
 }


